chore(filter-tags): pre-process filter tags

[ivankatliarchuk]

Description

This is a follow-up for a pull request #5060

In previous pull-request, I found a side effect for tags filter where Tag has no Key but only value set.
For me it looks like a bug that could be a feature. Let me know if it should be supported. I've actually added the test to highlight this in previous pull request. If we keep the behaviour where key is empty and value is provided, I'll update the documentation and logic

Design of actual pre-processing was discussed here #5042

BenchmarkZoneTagFilterMatchBasic-16    	 2593248	       460.1 ns/op
BenchmarkZoneTagFilterComplex-16    	  754824	      1474 ns/op

Checklist

• Unit tests updated
• End user documentation updated

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[mloiseleur]

In previous pull-request, I found a side effect for tags filter where Tag has no Key but only value set.
For me it looks like a bug that could be a feature. Let me know if it should be supported.

TBH, I do not know. It looks like a bug to me, at first glance.
@Raffo @szuecs: wdyt ?